Polyrhachis ammonoeides

Quick Summary

• Difficulty: Medium
• Origin & Habitat: Coastal northwestern Australia, from Dampier to near Perth. This species lives in warm, semi-arid to subtropical coastal areas, nesting in the ground where summers are hot and winters mild ^[1][2].
• Colony Type: Colony structure is unconfirmed. The species nests underground and uses carton, but whether colonies have one queen (monogyne) or multiple queens (polygyne) has not been recorded in scientific literature.
• Size & Growth:
  • Queen: 9.68–10.43 mm ^[1]
  • Worker: 6.65–8.52 mm ^[1]
  • Colony: Unknown – estimated several hundred workers based on related Polyrhachis species
  • Growth: Unknown – likely moderate based on genus patterns
  • Development: Unknown – roughly 6–10 weeks at 24–28°C based on related Formicinae species (Direct studies on this species are missing, the estimate comes from other Polyrhachis in Hagiomyrma.)
• Antkeeping:
  • Temperature: Keep at 24–28°C, reflecting their warm coastal Australian habitat. A slight temperature gradient helps workers regulate. Room temperature within this range works, or use a heating cable on top of the nest if needed.
  • Humidity: Keep the nest substrate lightly moist but not waterlogged. Coastal northwestern Australia is relatively dry, so avoid overly damp conditions. Let the substrate dry a bit between waterings.
  • Diapause: Unknown – the species lives where winters are mild and temperatures rarely drop much. Watch your colony for seasonal slowdowns and adjust care accordingly.
  • Nesting: Ground-nesting species that uses carton to build nest chambers ^[3]. Provide deep soil substrate (at least 5–10 cm) for burrowing. Y-tong nests with soil chambers or plaster nests work well. Avoid acrylic nests – naturalistic setups are best.
• Behavior: Polyrhachis ammonoeides is calm and not very aggressive. Workers forage actively on the ground and low plants. They are moderate escape artists for their size – use standard barriers (fluon, tight lids) but they are not as likely to squeeze through tiny gaps as tiny ants. The genus often builds carton galleries, so they may create visible nest structures if given suitable materials. They probably use chemical trails and tandem running to recruit nestmates, as is typical for Polyrhachis.
• Common Issues: Limited availability – rarely found in the hobby due to its restricted range and poor documentation, Colony founding is slow – like many Polyrhachis, founding colonies may take time to establish, Escape risk exists despite moderate size – secure enclosures with tight-fitting lids, Carton nesting needs – must provide soil or other fibrous materials for nest building, plain artificial nests may not suit them, Temperature sensitivity – needs warmth, struggles below 20°C

Natural History and Distribution

Polyrhachis ammonoeides lives only in a narrow coastal band of northwestern Australia, from Dampier in the north to near Perth in the south ^[1]. This region has hot, dry summers and mild winters. The species was first described by Roger in 1863 from Port Jackson (Sydney), but that was a mistake – the real type locality is Western Australia. It was later misidentified as a separate species, Polyrhachis ammonoeides, by Forel in 1907,but Kohout synonymised them in 1994 ^[1]. P. ammonoeides belongs to the ammon species-group in the subgenus Hagiomyrma, which is known for having hooked petiolar spines and golden body hairs. It's an attractive ant with a black body, golden hairs, and dark reddish-brown legs and mandibles ^[2].

Nesting Behavior

This ant nests underground in soil ^[1][3]. Like other Hagiomyrma species, it builds carton – a kind of papery material made from chewed plant fibres and gland secretions – to strengthen its nest chambers ^[3]. Pupae are enclosed in cocoons ^[3]. In captivity, you need to give them deep soil substrate (at least 5–10 cm) so they can burrow. Naturalistic setups with soil or plaster nests work well. The carton-building behaviour means they may make visible structures if you provide suitable organic materials (e.g. small twigs, leaves) in the outworld.

Feeding and Diet

No specific diet studies exist for this species, but Polyrhachis ants are generally omnivorous. In the wild they eat honeydew, nectar, and small insects. In captivity, offer them a variety: sugar water or honey as a steady energy source, and protein from small insects like mealworms, crickets, or fruit flies. Feed protein 2–3 times a week and keep sugar water available. Remove any uneaten prey after 24–48 hours to prevent mould. Their moderate size (workers up to 8.5 mm) means they can tackle prey larger than what tiny ants would accept.

Temperature and Seasonal Care

Because they come from coastal northwestern Australia, P. ammonoeides needs warmth. Keep the nest at 24–28°C for best colony activity. They do well with a temperature gradient so workers can choose. If your room is cooler, use a heating cable on top of the nest (never underneath, as that dries the soil). Diapause is not confirmed – the species lives where winters are mild and temperatures rarely drop much. Watch your colony: if they slow down in winter, you can reduce feeding and let the temperature drop slightly (but not below 15°C). If they stay active all year, just keep consistent warmth.

Housing and Setup

For this ground-nesting species, a naturalistic setup works best. Use a formicarium with a deep soil chamber (at least 5–10 cm of substrate) or a Y-tong nest with soil chambers. Avoid acrylic nests. Provide an outworld for foraging and feeding. Use a water test tube as a humidity source – place it in the outworld or nest area with the cotton properly sealed to prevent flooding. For escape prevention, use standard barrier methods (fluon on rims, tight lids). These are medium-sized ants, so they won't squeeze through tiny gaps like minuscule species, but still secure the enclosure.

Frequently Asked Questions

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References